Resistor and method of making the same



Oct. 16, 1928.

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G. M. lLITTLE RESISTOR AND METHOD OF MAKING THE SAME Filed Sept. 27. 1922 INVENTOR George M. LiH'le.

WITN ESSES:

ATTORNEY sof Patented ct. 16, 1928.

UNIT-EDT STATES PATENT OFFICE.

GEORGE M. LITTLE, 0F PITTSBURGH, PENN SYLVANI'A,v ASSIGNQR TO WESTINGHOUSE ELECTRIC @tv MANUFACTURING-COMPANY, A CORPORATION 0F PENNSYLVANIA.

RESISTOR AND IllllIIiiTIzlKjl')- OF MAKING THE Application tiled' September 27, 1922. Serial No. 590,753.

This invention relates .to resistors,l moreparticularly to resistors of the carbon-pile type and to methods of making the same.

It is common practice to utilize plates of carbon or of refractory-material containing carbon in contact vizitheaehother to provide a resistor for carrying current in electric furnaces.l The resistance thereof is caused mainl by-the poor contact between the plates. guch resistors have advantages in that they are'capable of withstanding a considerable amount of heat without softening, melting, volatilizing or otherwise de! teriorating in service.. However, they are expensive tol manufacture, require a consid/- erable time to 'assemble and are relatively fragile and subject to breaking in handling and service.4 t i The present 'invention is directed to a resistor of this type, it being among the objects thereof to provide a carbolrpile resistor which shall be simple in construction,I inexpensive to asesmble and eicient in service.

In` practicing myy inventionf providea series of plates. made of plastic material such as coke, pitchand oil thoroughly mixed and pressed in close contact with each other in the plastic @state and baked in the as-- sembled position. The several layers of material constituting the4 plates are prevented from^ sticking together by various means. .A To accomplishthis, the surface of` av plate may be cooled, wetted, or dusted with suit-able materialand the next layer placed thereon. To insure the latesholde ing together while being baked, may mold small pieces of iron wire or strips of asbestos therein. j 1

My resistor may be produced in the following manner. I provide a wooden mold of the sizel and contour of the finished relsistor. I then'make a plastic mass by melting 35 partsof coal-tar pitch, adding 100 parts of calcined petroleum coke powder and alittle summer oil thereto and then heating and mixing the ingredients. A sufficient. amount of the lastic mass is tamp'ed into the mold to provide-a plate of anydesired thickness. The exposed'surface thereof is thon treated to4 render the same nonadherent in any suitable manner. The surface may be either cooled, moistened with a little water, or coke dust,l lampblack, powdered graphite or the like may be dusted thereon. Another portion of the plastic mass is then tamped in and the steps are repeated until the desired number of plates have been formed. The .assembly is then removed from the mold and baked in an oven to the desired degree.

This method provides a resistor in which the irregularities in the contacting surfaces of adjacent plates are complementary, thus Yavoiding an uncertain fit between plates and obviating the necessity of `assembling the plates after baking. The cost of a structure of this lkind is materially less than that of f resistors of the old type. l

' Inorder to obtain a resistor which shall have a high resistance and great mechan- Fig. 1 is a cross-sectional view of a resistorl made in accordance with my invention, and

Fig. 2 is an enlarged cross-sectional view of a portion thereof, showing the irregularities in the surface of the plates.

I provide plates l of a relatively hard resistor material and assemble between alternatelplates l thepla'tes 2 of resistor materialwhich are soft and have a relatively higher resistance than plates l; 4; having suitable terminals 5 secured thereto, make ycontact with the end plates of the carbon pile thus formed.l

My new method of forming ,all the plates offa resistor simultaneously results in a structure, in'which the irregularities 6 of adjacent plates interlock and provide a construction in which the plates make contact over' substantially the entire surfaces thereof.

Although I have described lmy invention, setting forth certain details of construction and a composition which Inlay utilize, it is to be understood that my invention is not Electrodes 3 and*` limited to such details. For instance, compositions other than that described are suitable for my purpose and all of the plates may be of the same material or a'plurality of compositionsmay be utilized for the several plates. The irregularities 6 in the surfaces of the plates are those occurring normally in the manufacture thereof but, if desired, I may utilize a plunger adapted to stamp depressions into the surfaces of the plates to lock the same together. These and otherchanges may be made in the details of construction of my invention' Within the scope thereof.

I claim as my invention:

1. A resistor comprising adjacent contacting plates of resistor material, the irregularities in the contacting surfaces of adjacent plates being complementary, alternate plates of said resistor being of different types of resistor kmaterial.

2. A resistor comprising adjacent contacting plates of carbonaceous resistor material, alternate plates being hard andv soft.

3. A method of making resistors'vvhichv comprises providing a| plastic mass of resistor material, molding a plate therefrom, rendering the surface of said plate non-adherent and molding another plate thereon.

t. A method of making resistors which comprises providing a plastic mass of resistor material,- molding a plate therefrom, rendering the surface of said plate non-adherent, molding another plate thereon, and repeating the cycle of operations.

5. A method of making resistors Which comprises providing a. plastic mass of resistor material, molding a plate therefrom, covering the surface of said plate with material capable of rendering the same non-adherent and molding another plate thereon.

6. A method of making resistors Which comprises providing a plastic mass of resistor matcral, molding a plate therefrom, covering the surface of said plate with carbon dust to render the same-non-adherent, and molding another plate thereon.

7. A method of making resistors which comprises providing a plastic mass of resistor material, molding a plate therefrom, covering the surface of said plate With carbon dust to render the samc-non-adhercnt, molding another plate thereon and repeating the cycle of operations. y

8. A resistor comprising adjacent contacting plates of resistor material, the irregularities in the contacting surfaces of adjacent-plates being complementary, alternate plates beng composed of hard resistor material cons'sting mainly of carbon and the remaining plates being composed of soft resistor material consisting mainly of carbon.

9. A resistor comprising adjacent contacting plates of resistor material of different degrees of hardness, alternate plates being composed ofhard resistor material containing a substantial amount of carbon and the remaining plates being composed of so tt re- .sstor material containing a substantial amount of carbon. In testimony whereof I have hereunto subscribed my name this 21st day of September 1922.

GEORGE M. LITTLE. 

